1. Technical Field
The present invention in general relates to a welding fixture, More particularly, the present invention relates to an internal fixture for supporting a joint between two tubular workpieces, and retaining the two workpieces relative to one another while the workpieces are being joined by a process such as welding.
2. Discussion
Welding fixtures are often employed during a joining operation of two workpieces, such as welding. The welding fixture serves to temporarily retain two or more workpieces relative to one another. Preferably, the welding fixture also functions to support the joint formed between the two workpieces during the joining process. Various tools have been previously devised in attempts to permit one workpiece to be temporarily aligned and supported with a mating workpiece while the two workpieces are fixedly secured together by a joining procedure. While such devices have proven to be commercially acceptable for a wide range of applications, either alone or in cooperation with additional clamping devices, all are subject to improvement.
One known device is described in commonly owned U.S. Pat. No. 5,285,947, which issued on Feb. 15, 1994 and is entitled Welding Fixture. U.S. Pat. No. 5,285,947, expressly incorporated by reference as if fully set forth herein, is directed to an internal welding fixture adapted to assist in the joining of two tubular workpieces. The fixture includes a first group of extendable shoes driven by a first actuator and a second group of extendable shoes driven by a second actuator. The shoes cooperate to form a substantially continuous backup along the joint formed between the two workpieces. The first and second groups of shoes can independently retract to an interleaved position.
While prior devices have satisfactorily operated in most applications, disadvantages are inherent in these same devices under particular circumstances. In this regard, a need remains for a welding fixture adapted to temporarily retain a first tubular workpiece relative to a second tubular workpiece while the first and second workpieces are permanently joined which is controlled by a single actuator and can be axially centered with respect to one of the tubular workpieces. Most previously developed tools are generally unsuited for supporting the joint between the two workpieces as the workpieces are rotated and exteriorly welded. For example, in such applications, most prior welding fixtures require contact with the exterior of the workpieces, thereby interfering with the welding procedure. Furthermore, many previously developed welding fixtures are weight prohibitive in that they are unsuitable due to the damage they would cause where the workpieces are constructed from light weight metals, such as aluminum, or very thin metal. Other previously developed welding fixtures are also unsuited to substantially continuously support the joint formed between two tubular workpiece sections by only engaging the interior perimeters of the sections.
Still yet, other previously developed welding fixtures require multiple actuators for complete internal joint backup of tubular workpieces and are not adapted to axially center themselves with respect to a tubular workpiece.
It is therefore a principal object of the present invention to provide a welding fixture which is capable of quickly and accurately securing two tubular workpieces temporarily relative to one another from the interior of the workpieces, without the aid of any other clamping mechanism or support device.
It is a further object of the present invention to provide an internal welding fixture sufficiently light so as to not damage thin wall tubing.
It is still a further object of the present invention to provide an internal welding fixture which substantially provides continuous support about the perimeter of a joint formed between two axially aligned tubular workpieces.
Yet still another object of the present invention is to provide an internal welding fixture adapted to conform the perimeter of a generally tubular workpiece to a uniform radius of curvature.
Another object of the present invention is to provide an internal welding fixture which provides accurate internal alignment and reforming of pipe while reducing fit-up times.